1. Field of the Invention
The present invention is generally related to an adjustment system for an engine and, more particularly, to an adjustment system which limits access to an idle fuel mixture screw.
2. Description of the Related Art
U.S. Pat. No. 5,603,869, which issued to McNew et al. on Feb. 18, 1997, describes a fuel mixture limitation device. The device limits post-adjustment rotation of an adjustment screw on single adjustment screw carburetors. On one embodiment, the limitation device uses a limiter cap removably attached to the adjustment screw which works in conjunction with a limiter stop attached to the carburetor.
U.S. Pat. No. 5,635,113, which issued to Walsh et al. on Jun. 3, 1997, describes a carburetor adjustment screw apparatus. The apparatus is intended for use with a diaphragm-type carburetor and it comprises a screw member having a shaft and a head by which the shaft may be rotated, with a generally tubular open-ended housing surrounding the head of the screw member. A cap member is mounted in the housing and is movable axially of the screw member between a first position and a second position.
U.S. Pat. No. 5,753,148, which issued to King et al. on May 19, 1998, describes a carburetor needle valve adjustment limiter cap apparatus. The limiter cap has a hollow cylindrical outer body of rigid material. It carries a limiter arm. A spring steel hollow retainer clip sleeve is telescopically received in the body and has inwardly and outwardly protruding resilient barbs reversely oriented relative to one another to respectively engage the cap body and the needle valve shank to respectively prevent retrograde relative telescopic motion between the clip and the body and between the clip and the valve shank.
U.S. Pat. No. 5,984,281, which issued to Hacker et al. on Nov. 16, 1999, describes a carburetor needle valve and limiter cap installation and adjustment apparatus. It describes an improvement in a limiter cap holder wherein the clip spring legs are interconnected by a spring web that flexes to accommodate flexing of the clip legs free ends during insertion of the associated limiter caps into the retaining clip and prolongs the effective friction grip service life of the clip.
U.S. Pat. No. 6,691,988, which issued to Warfel et al. on Feb. 17, 2004, describes a tamper resistant carburetor mixture needle. The adjustment screw arrangement is intended for use with a carburetor. The arrangement includes a carburetor body having at least one air/fuel adjustment screw threaded therein. The adjustment screw has a threaded shank and a head portion. The head portion is defined by a smooth top surface and an undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven side surface capable of being engaged and mated by an adjusting tool having a complementary undulant, uneven surface for initial adjustment of the air/fuel mixture in the carburetor.
U.S. Pat. No. 6,708,959, which issued to Dow on Mar. 23, 2004, describes a carburetor valve assembly. It has a plastic cam body connected to a plastic shaft which extends into the carburetor body and valve head press-fit into a slot formed through the plastic shaft.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Environmental restrictions require that threaded adjustment needles of carburetors be protected from improper manipulation. These regulations are intended to prevent the users of engines from improperly calibrating the idle fuel mixture ratio and, as a result, causing an engine to emit excessive pollutants. Most of these protective devices also inhibit the proper adjustment of the idle fuel mixture screw by a trained technician, such as the personnel of an engine repair facility. As a result, the adjustment of the idle fuel device requires excessive effort on the part of the skilled technician.
It would therefore be significantly beneficial if a device could be developed which inhibits the adjustment of the idle fuel screw by unqualified personnel while allowing the proper adjustment of that idle fuel screw by trained personnel whose responsibility it is to properly calibrate the engine and appropriately set the idle fuel adjustment screw.